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144 Charles A. Lane
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<br /> landscaping and plantings can be designed to What structural systems and materials should be
<br /> maximize privacy and wind/sun protection. Other site considered in planning an earth-sheltered home?
<br /> considerations such as vehicle and pedestrian access, The structural parameters of an earth-sheltered
<br /> utility hookups, easements, wells and septic systems home are probably among of its least understood •
<br /> usually pose no special problems for the earth- aspects, especially for the nonprofessional, individual
<br /> sheltered home builder. home builder. Yet,surprisingly, it is the area in which
<br /> A good knowledge of soil and groundwater many novice builders seem least willing to seek
<br /> conditions is very important in planning an professional help.
<br /> earth-sheltered house, but often prospective builders The stresses produced on an earth-sheltered house
<br /> will choose a site without any knowledge of where are far greater than those on a conventional
<br /> the groundwater table is located, how the soil above-grade, platform-framed house, and are far
<br /> transfers moisture (the percolation rate), the soil greater than a novice builder may suspect. The
<br /> composition (sands, gravels, clays, peat, fill,etc.),and structural design of a conventional home allows more
<br /> the chemical characteristics of the soil. Sometimes flexibility in precision and in the use of materials.
<br /> sod conditions can be approximated by contacting Thus, detailed structural engineering is usually
<br /> neighbors on adjacent lots, or by obtaining soil required in designing an earth-sheltered house.
<br /> surveys for the immediate area. If these methods do Structural systems and materials vary widely, and
<br /> not yield sufficient information, it is advisable to have included: cast-in-place reinforced concrete,
<br /> invest in a thorough soils test from a reputable soil reinforced mason •
<br /> testing firm. ry, precast concrete, post-tensioned
<br /> concrete, treated wood foundations, wood beam
<br /> In earth-sheltered housing, the surrounding soil is a roofs, fiberglass reinforced masonry, fiberglass,
<br /> functional part of the house, and not merely a design reinforced wood panels, concrete silo block, and steel
<br /> afterthought. A builder should be familiar with the and concrete drainage units. Little standardization in
<br /> properties of the soil, just as he would be familiar construction of earth-sheltered housing has yet been
<br /> with the properties of the other construction developed, and as a result, builders are faced with the
<br /> materials.
<br /> uncertainty that accompanies any prototype design.
<br /> Under optimum conditions, the soil should This lack of standardized construction techniques
<br /> provide good load-bearing strengths, good drainage makes builders reluctant to invest their efforts in
<br /> characteristics, and a sufficient distance between the earth-sheltered house construction, and can add to
<br /> house structure and the highest point of any construction costs once the decision to build is made. •
<br /> groundwater table. A wise builder should probably
<br /> avoid building in a flood plain area, in humic soils, or Care must be exercised to use the materials
<br /> in extremely expansive clays. properly. In flat roof structural systems, roof
<br /> clearance spans will vary with the type of material
<br /> Earth-sheltered homes are proving highly adaptable
<br /> used. Wood beam roofs obviously will require limited
<br /> to the urban setting as well as the rural setting.
<br /> Conditions of adjacent sites and structures are shorter spans than will a concrete material roof. To
<br /> more important in urban than rural sites: care must resist stresses developed by earth-bermed walls,shear
<br /> be taken that adjacent structures do not shade the walls should be designed and integrated into the
<br /> house plans. In two-story earth-sheltered homes, the
<br /> site. In some earth sheltered house designs, the
<br /> greatest stresses developed by earth-bermed walls,are
<br /> soil-berming may require a fairly large lot, thereby
<br /> making some smaller urban lots unacceptable. located at the intermediate floor. Too often. novice
<br /> On the other hand, urban sites considered builders overlook this fact and plan for a wood joist
<br /> undesirable for conventional homes may be ideal for intermediate floor system;in some cases,a wood joist
<br /> earth-sheltered construction, as soil-berming can be floor system is inadequate to safely transfer these
<br /> used effectively to block out unwanted views and lateral wall stresses.
<br /> noises. An excellent example of such use of an urban Another major class of structural systems, arches
<br /> site is the Seward West Redesign earth-sheltered and shell shapes, can transfer heavy loads very
<br /> townhouses in Minneapolis, Minnesota. Scheduled for efficiently. It is important, however, not to seriously
<br /> completion in late 1979, the 12 units are bermed to alter these simple shapes in a house design:therefore
<br /> the north side, which is adjacent to a noisy freeway; the placement of openings such as doors, windows
<br /> and the south exposure is open. A potentially and atriums in arches and shells should be done by a
<br /> objectionable housing site thus has been made useful competent architect and engineer.
<br /> through good earth-sheltered design [1 j . At present, professional builders need to develop a
<br /> Urban sites may also become more popular as better knowledge of loads and stresses caused by
<br /> automobile transportation costs continue to rise. earth-berming. As builders develop'more confidence •
<br /> With reductions in the costs of both transportation and variety in their products, the number of
<br /> and home energy use, earth-sheltered home owners cost-competitive designs available to the consumer
<br /> can significantly lower their energy expenses. should increase.
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